[mythtvnz] Myth & Raid. SW or HW..

[criggie]

On 18/07/12 20:42, Johan Schuld wrote:
> A while back the HD on my mythbox died and had to replace it with an old
> 250Gig ATA drive I had lying around. Not the best option with HD
> recordings etc.
>
> So, as HD will inevitably die, my plan is to buy some new HD's and put
> them in a RAID array. Thinking RAID1 as I currently don't have the funds
> to buy more than 2 drives.

All storage will die eventually.  Thats why you backup the stuff you 
can't replace,


> I've done quite some research so far about the options and wondered what
> the easiest and most reliable solution. I.e. I know people having a HW
> Raid using a Dell Perc 5/i card. These are so common they can be picked
> up for less than $100NZ inc shipping from ebay and with some SAS to SATA
> cables they run fine with SATA drives.  A cheaper option would obviously
> be SW Raid, but not that much cheaper.
>
> Regardless of SW or HW, I'm thinking of 2x 2TB drives, in Raid1. I've
> been looking at the WD Green ones as they are competitively priced and
> silent (pc is under the TV). That drive has been discussed many times
> here so I am aware that they might have issues in SW raid, I'm just
> still looking at a similar drive from another vendor.
>
> As Raid1 is really not that much overhead, should I just not bother with
> HW raid, and let linux do the job? (Opensuse 12.1) . Can I transfer a
> already existing non-raid install to a SW raid1 config? For now I'll run
> the OS and media storage on one raid volume, I might split that out
> later when I can afford some more drives.
>
> I can find quite some info about Raid, but not so much in combination
> with Myth.. don't want to do stuff that's overkill, but like to have
> stuff that works (particulary when one drive fails ;)


I've avoided green drives myself.  They've never been good fullstop, let 
alone with raid on top.

You can raid1 the OS if you want, but don't bother with raid anything 
for your TV recordings.  You're not trying to save these files forever.
If theres something broadcast that you do want to keep, write it to DVD 
or export it to AVI and put it with your important data.

So I'd suggest this:

sda 2TB drive |   100 GB     |      1700 GB                            |
sdb 2TB drive |   100 GB     |      1700 GB                            |

Create a raid1 for OS/mysql/exported videos out of sda1 and sdb1
So root is on /dev/md0 instead of /dev/sdXN

And use the 2x 1700GB as Mythtv's Storage Groups.  So its effectively a 
raid0 on those two partitions, but if a single drive dies you only loose 
half the files not all the files.

Software raid is faster than cheap hardware raid on a modern CPU (that's 
anything later than a P4)

Good hardware raid cards cost more than your entire system.
Excellent hardware raid cards cost more than a car.

Adding capacity in the future is a doddle - you add drives, tell myth to 
use sdc/sdd... as more storage group locations and its all done.

Just remember, its only TV - not worth overengineering.


-- 
Criggie

http://criggie.org.nz/